Embroidered paper-based electrochemical wearable device for pH monitoring in wounds

Herein, we report the first electrochemical microfluidic thread/paper-based analytical device (μTPAD) by harnessing the synergistic combination of embroidery as a manufacturing technique and paper-based technology. The effectiveness of the μTPAD was tested for potentiometric pH monitoring in chronic wounds. A configuration was designed for multiple analyses in chronic wounds, simply by cutting off one of the μthread-paper pads used for measurement and renewal every time the electrochemical cell was used for measurement. The electrochemical cell was constituted by conductive silver threads coated with graphite and Ag/AgCl inks, for the working and reference electrodes, respectively. The working electrode was also electrochemically modified with an iridium oxide film to sense proton activity, and the modified threads were then embroidered onto filter paper as a support. The μTPAD was successively connected to a portable miniaturized potentiostat, connected via Bluetooth Low Energy to a smartphone, with a dedicated app for potential readout to deliver a wearable device, allowing for pH monitoring in the pH range between 4 and 8, with a sensitivity of 0.056 ± 0.002 V pH^-1 and a reproducibility (RSD%) equal to 8%. The accuracy of the wearable device was assessed by measuring the fluid secreted in a chronic wound near the fibula of a human leg and comparing the data with a laboratory pH meter, demonstrating the reliability of this new concept of wearable paper-based devices.